I've encountered some strange behaviour since the 1.9.9 update: covers are rarely actually full screen (I've only experienced this with 2 books), and instead of most covers having the very narrow white border only on the right side, I now usually have significant white strips on both sides, with the cover image being squished into the middle portion of the screen. These borders are also seen in the thumbnails images in the library. Has anyone else been seeing this behaviour? I only use side loaded books, via Calibre and direct transfer.

I have noticed that the covers for side-loaded EPUBs do not fill the entire screen ever since the firmware release which changed the way covers were displayed in the sleep and off state i.e. in my experience only the covers for Kobo EPUBs fill the entire screen and the behavior for side-loaded EPUBs has not changed for recent firmware releases.

They filled the entire screen on my Kobo, except for the 1mm or so wide white strip on the right which has been mentioned here before. Since 1.9.9 I have white borders on both sides (with like 80% or so of my books), and anything from .5cm to 2cm or so in width, so some random process changed how covers are handled in 1.9.9 (and now 1.9.10) for me. Who knows...

I made a couple of test because I actually added a cover editor in my app (see my sig) and I did test a couple of way to write the html file so the cover is stretched to fit the screen (even if it deforms the cover). What I tried (and should have worked is height="100% and width="100%" and it works ok in sigil and calibre and even ADE, but not on the kobo, it keeps the aspect ratio of the image (on the generated cover, the cover page in the book is displayed correctly).

I also did found out that I there was a change in recent updates, because I had a Storage Error (The very first) and copied all my books so I could but them in easily after the reset, but all my cover were screwed.

I asked in the Beta forum for any information to the dev to know if it was intentional or a bug and if it was intentional a way to format the html so that it could display properly, but haven't had any answer.

I just don't know if it is a bug, will it be fixed, is there a workaround. If anybody knows the answer to those question please give some insight, so I could at least update my tool so people could fix theirs.

When the KT processes an epub, it finds the cover image and creates 4 thumbnail images in the .kobo/images folder.

They are named with a complex pathname that includes the folders to the epub to which they refer.
N3_LIBRARY_FULL 355x500 pixels
N3_LIBRARY_GRID 149x223 pixels
N3_LIBRARY_LIST 60x90 pixels
N3_SOCIAL_CURRENTREAD 120x186 pixels

The files end in the extension "parsed" but are simply renamed jpg files.
You can view them by copying to your machine and renaming to .jpg.

In firmware versions up to 1.9.10 ( I have not tested 10 yet ) you could replace these files with your own image and the KT would use that image for sleep and power off covers etc.

The simplest method of ensuring that you have the correct filename is to open the actual file on the KT in an image editor and then simply copy the image you want over the original image and thus when you save, the correct filename is used. Note that you will likely have to resize the "canvas" of the original image to fit the new image if it is larger than the original.

I have tried images with up to 800x600 with no problem, though I only replace the big thumbnail most of the time. Yes, it will be VERY time consuming.

Please remember that the proportions of the KT screen and the proportions of the average paperback or epub cover are NOT the same so you will need to either add margins ( I suggest black ) or crop the cover.

Also, I had a reply on another post I made about this that they are looking into the method used to create the thumbnails. I suspect that this is way down on the list since it is simply cosmetic and not a functional problem.

Why I am doing is not modyfing the files from the Kobo, but the ePub itslef, before it gets processed.

But I have been thinking that I could maybe just resize the image to fit the screen ratio.

But the dimension you give are not the same ratio, the screen is 800 x 600 so a ratio of 1.333 should be used for the full page cover, but with the dimensions you are giving me I have a ratio of 1.4. And Every other one has a different one. I will have to do some testing for the correct ratio that could be perfect for all sizes.

I did some more checking tonite and there is a fifth thumbnail created. This is the one used for the sleep and power off screens and is 800x600 and does not get created until you open the book.

I did a test and what seems to happen is that the KT will leave an 800x600 image untouched ( except for dithering to grayscale ) but the width of the smaller thumbnails is squeezed to match the proportions of the particular thumbnail. Because the amount of distortion is small it is very difficult to detect.

I have not tried any cover images at other dimensions or proportions yet, for example 600x600 or 729x544.

NOTE: this firmware (1.9.10) uses a new algorithm for creating the thumbnails.

I have finally figured it out. To have your image fit your screen here are what you need to modify inside your cover html file. (with firmware 1.9.10)

First remove any style that are present in your file that could affect it, that means under the <head> element any <link> element that refers to a css and xgpt file. I also remove the <style> element under <head> just to be sure.
And as a precaution I added the following style (note that putting that into sigil will add a style tag inside the head, it does the same thing):

Code:

<body style="margin:0; padding: 0; border-width: 0">

Now the important part, I have only been able to have it work when the file is svg, so if it is not I convert it. To change the svg that calibre generates, just change the width and height (inside the <svg> tag, not <image>) to 600 & 800 (it usually puts 100%, this is what creates the problem, even with the ratio to none) and preserveAspectRatio="none" (the case is important).

Now when you load your book inside your Kobo it will process it and the cover created will fit nicely.

P.S. I have automated all this in my app, I will do some more testing and release a new version soon with this (should be v1.5.0), but note that I also resized the image to a ratio of 0.75 (600/800) just to be sure. Source is available right now.

Update : Even with the FULL file, there is still margins in the book I created, the above methods seems to work, no matter what.

Most covers are not set to take up the entire screen. They are set to be aspect ratio correct. Having the covers use the full screen is aspect ratio incorrect in most cases.

Yes but even with an incorrect aspect ratio, I would rather have a full cover. And I am sure that a little distortion will not be that big a deal to some. Also the fact that the way the cover are generated in the KT does not respect the aspect ratio already. I also think that most kepub are also distorted to fit the cover.

Anyway my program let's you choose whether to keep the aspect ratio or not. But at least there is a way to modify your file if you don't want those white bars.

New Calibre update with the ability to adjust covers simply by resending the book to the device solves the vertical squishing problem in library view, but not in sleep/powered off mode. No idea if it was even supposed to, just FWIW.